In recent times, the counter-top coffee maker has become a ubiquitous part of the average American household. These counter-top coffee makers use a simple water heating system to brew coffee. Water is poured into a housing reservoir, generally disposed at the top or rear of the coffee machine. The water comes into contact with a heating coil disposed at the bottom of the coffee maker, where it is heated and then flashed into hot water by a spout disposed over a funnel. The hot water is directed into the funnel containing ground coffee. The hot water impinges upon the coffee grinds, causing the grinds to release their flavor. A coffee carafe is disposed below the funnel. The carafe is heated by the heating coil in order to keep the brewed coffee warm. The funnel often contains a paper or metallized filter for preventing the grinds and coffee bitters from dropping into the carafe.
The reason that this type of coffee maker has become so popular with the American public is its ability to brew a good cup of coffee fairly quickly and without much effort.
The American public is very particular about the taste of its coffee; many individuals will often spend many dollars in the pursuit of the best coffee blends and the finest beans. The American public is so obsessed with obtaining the best coffee, that every nuance to bring the best cup of coffee to the table is marketed. For example, special acid-free paper is sold for the funnel, so that the brewed coffee will not be soured by trace amounts of sulfuric acid used in paper processing.
It has recently been realized that despite all of the efforts of the individual to make the best coffee, the final result is greatly dependent upon the local water used in the coffee maker. Tap water in many areas is contaminated with traces of metals and other impurities that impart a poor taste to the brewed coffee. Not every household has water purification devices to clean the water of these unwanted contaminants.
The present invention has, as one of its objectives, to provide a coffee maker that has a built-in water filter, the filter of which is conveniently disposed in the water reservoir ahead of the heating coil. Water passing from the reservoir to the heating coil must pass through the built-in filter, thus leaving behind the water-borne impurities.
The current invention also reflects the discovery that the built-in filter will eventually become saturated with the contaminants, and will require replacement or cleaning. One of the problems associated with replacing the in-line filter is determining when a new filter is needed. Normally, an expensive photo-sensor would be required to detect the change in color of the contaminant-saturated filter. The cost of such a sensor would be prohibitive in a household appliance.
The invention reflects the discovery that an average filter will last long enough to brew a predetermined number of pots of coffee, depending upon the purity of the tap water being used. Therefore, an easy way to determine when the filter needs replacement is to count the number of times the water-filling lid is opened. The counter is used as a filter age indicator. Filter replacement is indicated in the inventive coffee maker when the lid is opened the indicated, predetermined number of times.